EAA and Guiding/PEC

[Fir Chlis]

With some downtime due to cloudy night after cloudy night, I’ve been researching guiding (PHD2) and PE training/ PEC and was wondering if anyone doing EAA uses either of these - and if they are of noticeable benefit in EAA. 

My suspicion is that they are probably too much of an overhead in lost observing time, especially if you get infrequent clear nights, and may not have any noticeable benefit with the relatively short sub-frames used in EAA. 
 

I know that, in theory, once a PEC curve has been recorded you should be able to reuse it, provided that the mount (HEQ5Pro in my case) is parked and unparked but the occasional crash /disconnect that I get with SharCap /EQMOD would invalidate and necessitate re-recording. 
 

Guiding, of course, requires the expense of another camera, and I’m guessing that there’s another overhead in setting PHD2 to guide for each object you want to observe, which is going to eat into the observing time. 
 

Cheers 

 

Geoff

[PeterC65]

I don't do guiding for EAA. I have wondered about it but the consensus in the CN EAA Forum seems to be that it isn't worth it for EAA and as you mention, it would require more kit and more software.

I have experimented briefly with dither only guiding in SharpCap as I've read reports that it is useful, but it didn't make any difference for me and it was hard to get it to work. I usually use two scopes / cameras when I do EAA and SharpCap works by discarding frames when dithering which it can't do for the secondary camera so it may not be a good idea for me.

I operate the mount in AZ mode and as I understand it PEC is for EQ mode. I have considered trying EQ mode but that would limit me to one scope / camera and it feels like a lot of effort.

My EAA exposures are never more than 15s and so I think the only benefit I would get from any of these things would be smaller black edges as frames stack.

 

[PhilB61]

I would agree in general that the hassle may be greater than the benefits. However, it will depend to some extent on how accurately your mount currently tracks, what exposure times you use, and what focal length/image scale you are operating at. I suppose it comes don't to what issues do you have that you think guiding may resolve?If you are getting elongated stars, are you certain your polar alignment is accurate enough, could you reduce exposure length and just stack more?

If you want to try guiding I would forget about PEC for now and just get basic guiding running, setup your system to guide directly to the mount from your pc or device, don't do it via the ST4 port, otherwise you will have to recalibrate on every new target.

You will have to run a guide calibration at the start of each session if you break down your equipment. This will take about 2 -4 minutes, after that the time overhead will be about 30sec on each new target for the guider to acquire a guide star(s) and to settle. 

Be aware that touching the scope to alter focus, re-center etc may cause the guide star to be temporarily lost.

[Fir Chlis]

Following on from this, I’ve done an analysis of my mount’s performance using sets of raw frames that I took a few weeks ago. As it is SharpCap specific, but the procedure may be useful to others, the write up is on that forum. 

https://forums.sharpcap.co.uk/viewtopic.php?t=7630

Geoff

Edited April 19 by Fir Chlis

[PeterC65]

I'll give you process  try with my mount next time. It hadn't occurred to me to check the drift of stars within a frame to check what the maximum exposure time should be. Something I relly ought to do give I operate in AZ mode.